The rehearsal, led by the U.S. Department of Homeland Security, is code-named TOPOFF 5. Canadian troops were among the 15,000 participants involved in last October's TOPOFF 4 in Portland, Ore., Phoenix, Ariz. and Guam.

"Exercises provide unique training opportunities to strengthen our ability to deal with potential emergencies," said Public Safety Minister Stockwell Day in an e-mail statement responding to 24 hours' interview request. "They are important tools to strengthen Canada's ability to deal with real incidents."

An undated Public Safety Canada report said up to $22.8 million was needed to fund emergency management, counter-terrorism, cyber security and critical infrastructure protection exercises, "leading to a trilateral full-scale exercise prior to the Vancouver Olympic Games in 2010, as outlined under the Security and Prosperity Partnership."

SPP was founded in 2005 to promote economic growth and enhanced security in North America.

"Does it mean that if the American forces are training with Canadian forces that they are going to be positioned here in Canada during the period of the Olympic Games?" said 2010 Watch's Chris Shaw. "And, if so, under whose command?"